An electro-hydraulic (EH) valve is usually used to control the flow of hydraulic fluid in various hydraulic systems. For example, the EH valve may be utilized in a transmission system of a machine to control the flow of hydraulic oil in the transmission system. In another example, the EH valve may be utilized in a steering assembly of the machine to control the operation of the steering system. Due to wear and tear in such hydraulic systems, the quality of the hydraulic fluids, being circulated in such hydraulic systems, may degrade with time and usage of the machine. Other factors that may affect the quality of the hydraulic fluid may include, but are not limited to, oxidation of the hydraulic fluid, contamination of the hydraulic fluid, and consumption of additives by the hydraulic fluid. Contaminated hydraulic fluids may damage the EH valve.
Usually, the contamination of the hydraulic fluid in the hydraulic systems is monitored using a light source and photo detectors. The light source may be installed at one end of a flow path in the hydraulic system, and the photo detector may be installed at another end of the flow path. A beam of light is directed through the hydraulic fluid and its intensity is monitored by the photodetector to determine the level of contaminants in the hydraulic fluid. However, integrating light sensors (or photodetectors) in the hydraulic system flow paths may increase the complexity and a cost of the hydraulic systems.
PCT patent application WO9801739A2 (hereinafter referred to as '739) discloses a system to detect a quality of lubricating oil in an oil pan. An acoustic sensor, installed in the oil pan, includes a piezoelectric element that is configured to generate a wave signal. The wave signal propagates through the oil and is detected by the acoustic sensor. Based on the wave detected by the acoustic sensor, the quality of the oil is determined. However, the system disclosed in '739 requires a separate wave generating device and a separate sensor device. Accordingly, integrating such a system in hydraulic systems is complex (due to space constraints) and expensive.